A crude plant extract that was toxic to spider mites in a leaf dip bioassay was subjected to detailed chemical analyses using chromatographic and spectroscopic techniques The analyses revealed that the major active chemical was probably β-sitosterol-3-glucoside, a known phytosterol The literaturc indicates that this chemical has becn identified in a number of plant species and that it has been tested for utility in a number of medical therapies. It has not so far been assayed for the control of arthropod pests The data indicate that this compound may be of use in the control of pest species, especially spider mites.